1. Field of the Invention
This invention refers to apparatus for regenerating a drying agent in driers for gases and air under positive pressure.
Although the invention is equally applicable to both gases and air under positive pressure it will be more particularly described here in connection with compressed air.
As used herein, the term gas is intended to include but not be restricted to air.
Compressed air in utilized to a continually greater extent in various fields, for example in the engineering industry and in vehicles, such as trucks, buses, trains, etc. Increased requirements with regard to dryness and purity are placed on the compressed air that is utilized in these connections, as in practice it has proved that if the compressed air is too moist or contaminated it may cause unnecessary wear to tools and machines operated by it. In order to prevent this damaging effect as the result of moisture the compressed air is made to flow through so-called drying towers in which moisture is removed so that the compressed air exiting from the tower is substantially dryer than the compressed air that was introduced into it. The drying towers may contain various types of hydroscopic mass or a drying agent. When moist air to be dried flows through the drying towers its moisture is given off to the drying agent, and the drying agent therefore has to be regenerated, i.e. dried out, so that it may be utilized again. Such drying can for example be performed by conveying part of the dried air leaving a predetermined drying tower to another drying tower which contains a drying agent which is to be dried, wherein this supplied air is permitted to pass through the drying tower and to absorb moisture from the drying agent before the relevant air is delivered from this second drying tower.
2. Description of the Prior Art
In known structures of the relevant type heating of the compressed air that is utilized for removing moisture from a drying agent has been carried out for example by disposing an electric heating coil directly in the moisture-absorbing mass in the drying towers or alternatively by placing a heating coil in a container located outside the drying tower and permitting the heating coil to heat the air contained in said container, whereafter this air is introduced into the drying towers as drying air. However, in the first-mentioned of these cases, the disadvantage occurs that in practice the heating coil corrodes fairly soon, whereas the second solution is uneconomical, as it results in a substantial loss of heat.